The present invention relates to a base structure for a mobile access platform.
Access platforms generally have a cage for an operator that is mounted on the end of a hydraulically-operated boom. The boom is mounted on a base structure and can be moved up and down or from side-to-side under the control of an operator in the cage.
There are two main types of access platform. The first of these is mounted on a trailer and has stabiliser legs that may be brought into engagement with the ground to stabilise the platform. This type of platform cannot be moved during use.
The second type of access platform is provided with wheels and is fully mobile. It does not have stabiliser legs and is stabilised solely by the weight of the base unit and the counter-weight attached to the boom. This type of platform is normally self-propelled and may be driven from the cage even whilst the boom is raised. The present invention relates to mobile access platforms of this general type, in which the base unit does not have stabiliser legs.
In mobile access platforms, the wheels are normally mounted on rigid axles without any form of suspension and the tyres are very hard. This is essential to ensure that the base unit does not tilt when the boom is extended to one side of the base and to provide the necessary stability. The base unit must also be very heavy, and the wheels and tyres normally provide a significant part of the weight of the base.
One disadvantage of providing a completely rigid chassis with no suspension is that when the mobile access platform is standing on a slightly uneven surface, one of the wheels may be raised slightly off the ground. Whilst this does not seriously affect the stability of the platform, since the weight of the lifted wheel still contributes to the overall weight of the base, it can be disconcerting for the operator. Also, if the lifted wheel is a drive wheel, drive from that wheel will be lost.